Drizzle of the coastline of Maderia

Heavy drizzle on the north side of Madeira

22 October 2021 12:00 UTC

Drizzle of the coastline of Maderia
Drizzle of the coastline of Maderia

Warm rain clouds over Madeira in October 2021 could easily be identified in the Meteosat and GOES Day Microphysics RGB product.

Last Updated

23 November 2021

Published on

09 November 2021

By Jochen Kerkmann (Germany) and Ivan Smiljanic (CGI)

On 22 October, the Portuguese island of Madeira was situated at the eastern edge of the Azores High, under the influence of the north-easterly trade winds (Figure 1). The typical Madeira weather in this situation is cloudy/overcast on the north side of the island and sunny with patches of stratocumulus clouds on the south side, where the capital Funchal is located.

In the Airmass RGB, the low clouds around Madeira have a green colour, but there isn't a good contrast to the cloud-free areas which also appear in shades of green (note that the Airmass RGB has not been designed to monitor low-level clouds).

Meteosat-11 Airmass RGB and ECMWF geopotential height 850 hPa, 22 October 12:00 UTC
Figure 1: Meteosat-11 Airmass RGB and ECMWF geopotential height 850 hPa, 22 October 12:00 UTC. Source: EUMeTrain.

More details of the cloud situation around Madeira can be seen in Figure 2, which is a comparison of the High Resolution Visible (HRV) channel with the Day Microphysics RGB product. The north side of the island and the central regions appear totally covered in cloud, while on the southern side cloud-free patches can be seen. In addition, the dark magenta/violet colour of the clouds in the Day Microphysics RGB on the north side of Madeira hints at warm rain/drizzle (rain from water clouds), probably enhanced by the orographic blocking effect of the island. The clouds directly to the north of Madeira also have the same violet colour, so it was probably also raining there.

Meteosat image comparison

Meteosat-11 HRV compare1
compare2
 
Figure 2: Comparison of Meteosat-11 Day Microphysics RGB (left) and HRV (right), 22 October 12:00 UTC. Source: EUMeTrain.

The different weather on the north/south side of the island can be seen in ground pictures taken at Cabo Girao (Figure 3, south side, 10:00 UTC) and at Cascata Agua d'Alto (Figure 4, north side, 13:00 UTC) during a 'West Tour' of the island. While on the south side there was plenty of sunshine, the weather on the north side was quite unpleasant with heavy drizzle at times.

South coastline of Maderia
Figure 3: Weather on the south side of Madeira, at Cabo Girao, 22 October 10:00 UTC.
North coastline of Maderia
Figure 4: Weather on the north side of Madeira, at Cascata Agua d'Alto, 22 October 13:30 UTC

A 20-minute timelapse, taken at the Cascata Agua d'Alto (Figure 5), shows the blocking effect of the island, the clouds sloping upwards on the steep north coast. The drizzle can also be seen in the timelapse.

Figure 5: Timelapse of clouds and drizzle at Cascata Agua d'Alto, 22 October 13:10-13:30 UTC (4-sec intervals)

Finally, Figure 6 is a comparison between the Meteosat-11 and the GOES-16 Day Microphysics RGB products. As can be seen, despite different techniques to derive the RGB product (different formulas for the solar component of the IR3.9 channel), the RGBs look quite similar, except for the parallax from the different viewing angles and the different horizontal resolution (Meteosat-11 3km, GOES-16 2km).

Meteosat and GOEs image comparison

GOES-16 Day Microphysics RGB compare1
compare2
 
Figure 6: Comparison of Meteosat-11 Day Microphysics RGB and GOES-16 Day Microphysics RGB, 22 October 12:00 UTC. Source: EUMeTrain.

For more information on the RGB, there is a Quick Guide of the Day Microphysics RGB product.

Note: this important application of the RGB product (detection of warm rain) is NOT covered by the guide. The guide focuses on the weather/clouds in continental Europe where warm rain clouds are seldom observed. Warm rain is more of a typical feature of maritime stratocumulus and of low level clouds in places such as the south west peninsula of England (especially Cornwall) or Central Africa. Also, the RGB Colour Interpretation Guide, which includes currently 14 examples of the Day Microphysics RGB, does not show the typical colour (violet) for warm rain clouds. The colour will be added in due time, using one of the examples in this slideshow (zipped file) .

 
 

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Timelapse taken at Porto Moniz on 22 October at 12:00-1220 UTC
Timelapse taken near Cabo Girao on 23 October at 17:40-18:05 UTC
Timelapse taken at Funchal on 24 October at 09:00-09:40 UTC
The weather in Madeira explained (Madeira Exclusive)
Catastrophic flash flood on Madeira Island (EUMeTrain)